Here's the good part ~ the earliest dates are 12,000 BC. That's right there 1000 years BEFORE the Younger Dryas.
It would take another 5,000 years before people redeveloped an ability to cut stone like that as a general practice.
Whatever happened it was a total wipeout!
A meteor hit the earth around 10,000 BC it was huge...causing tidal waves throughout the earth and quakes...it took 200 years for the atmosphere to clear up. It took out Atlantis and what humans, enosh etc that were left migrated into the Egypt area. That was about the only place that the atmosphere was livable.